Spectroscopic Ellipsometry is a non destructive optical technique that is based on the measurement of the change of the light polarization state and provides information for the optical, and not only, materials properties. Spectroscopic Ellipsometry can be used for the in-situ and real-time monitoring during growth of inorganic and organics thin films, for the determination of the mechanisms that take place during growth and for the change of optical properties and substrate properties under various processes.[1]
In semiconductors, insulators but also in metals, bonded electrons with the absorption of a photon from electromagnetic radiation, are excited or undergo interband transitions, which are responsible for the strong absorption in the Vis-FTV spectral region. The application of Spectroscopic Ellipsometry technique, with the use of Synchrotron radiation, gave the possibility of spectroscopic measurements in an energy range up to 9.5 eV, that could not be covered with compatible light sources that are used in lab scale and the verification of the absorption and electronic structure of oxides and transparent materials in FUV spectral area[2-3] Thus, spectroscopic study of materials that show optical transparency in the area of Visible and Near Ultraviolet, such as Silicon Nitride (SiNx), was realized.[2] Moreover in combination with techniques that are used for the determination of the materials composition, the correlation of optical constant and properties was determined. Optical quantities, such as the energy in which appears the maximum electronic absorption in a composite material, known as mean Gap or Penn Gap (E0), and the energy where the edge of electronic absorption appears, known as the fundamental optical energy gap (Eg), are the ones that are directly related with their composition. [2-3]
The correlation of optical constants, determined by Spectroscopic Ellipsometry, with other important properties, such as stoichiometry, has been certified also for metallic composite films such as Titanium Nitride films (TiNx), for which the plasma energy ωp is correlated with the stoichiometry x. [4-5] The ωp is calculated from the Spectroscopic Ellipsometry spectra in the energy region of the dielectric function and is the energy for which the real part of the dielectric function is equal to zero [∈1(ω=ωp)=0]. With the application of in-situ and real-time ellipsometry in the area of visible and Near Ultraviolet, during TiNx films growth, it was possible the real-time determination of the stoichiometry and thickness of the films TiNx.
Moreover, with application of in-situ and real-time ellipsometty in the area of Infrared, during transparent films Silicon Oxide (SiOx) growth on substrates of crystalline Si, the determination of deposition rate was realised. [6]
Methods for the control in production line of thin films and coatings with priority in the properties of the surfaces, interfaces and layers or thin films that are related to the functional properties of the intermediate and final products are not available aid do not represent existing technologies. The lack of control systems in production line that would be used for the modification and the deposition of thin films onto polymeric surfaces, in combination with the fact that there is transfer of the quality control from the control of the final product to the control during production, requires the improvement of production line performance. This is very important since the deposition processes is comprised of several stages (e.g. surface modification/activation, inorganic or organic coating deposition). Therefore, an appropriate, smart and reliable control process must: a) control the technical requirements for coatings (e.g. good adhesion of the substrate) in new applications, b) provide material and energy reduction and c) keep low the cost of combined processes.